The present disclosure relates to colorimetric detection. In particular, the present disclosure relates to the use of printable composite materials for colorimetric sensing applications.
There is a continuing need for simple, rapid and inexpensive point-of-collection detection assays for a variety of applications such as monitoring of food and water for toxic contaminants, diagnostic applications, and environmental analysis. Such assays are particularly useful in the developing world where expensive instrumentation and/or specialized expertise for standard sample analysis are prohibitive. These assays would also have the benefit of reducing the time and costs associated with sample transportation and storage as well as providing the convenience of immediate results for rapid decisions on-the-spot (e.g., detection of blood alcohol content through the point-of-collection Breathalyzer test allowing a police officer to arrest an individual immediately).
Colorimetric assays are one form of point-of-collection testing that is rapid, inexpensive and requires little to no training or instrumentation to perform. Colorimetric test strips are currently on the market for a variety of applications such as pH measurement, measurement of blood glucose and triglycerides (see, for example, U.S. Pat. No. 7,214,504, which is incorporated herein by reference in its entirety), albumin measurement in urine (see for example, Canadian Patent Application No. 2,585,816, which is incorporated herein by reference in its entirety) and analysis of free chlorine (see for example, U.S. Pat. No. 5,491,094, which is incorporated herein by reference in its entirety). In some forms, the technology behind these strips is largely based on existing colorimetric indicator molecules such as Coomassie Blue for albumin. Such molecules may be of limited utility and are not universal for any analyte of interest. Alternatively, some strips are based on enzymatic reactions (e.g., lipoprotein lipase and 4-aminoantipyridine for triglyceride detection) which require the production of purified proteins, making manufacture costly to scale-up.
An emerging class of colorimetric assays utilizes surface plasmon resonance (SPR) of nanoparticles as the source of color change to report the presence of a target analyte (see e.g., U.S. Patent Application No. 2014/0220608, Canadian Patent Application No. 2,812,312, and Chinese Patent Application No. 100510704). However, only a small portion of these assays are provided in a paper-based test strip.